In the viewer it looks correct and also when rendering this frame manually it comes without glitches.
Edit:
Just tested with newest build (RC15), issues is still present.
Workaround is rerendering the frames with the wrong DropShadow, since the glitch is not in DiskCache.
So, is the issue only with DropShadow? Do you get the same issues with other PyPlugs, or OFX? If you create a new project with a solid (or whatever) and DropShadow, do you get the same issue? I’m looking for something that can easily be replicated.